The aforementioned attributes notwithstanding, the turbo-shaft engine is not generally utilized to provide power in common conveyances such as boats, motorcars and, trucks. This is largely because a turbo-shaft engine is expensive to build, as much as ten times as expensive as reciprocating Otto and Diesel cycle engines of the same horsepower. This expense can be attributed largely to the exotic metals and other materials that are needed to handle the extreme temperatures present in the turbo-shaft engine. Additionally, the turbo-shaft engine cannot change its speed of rotation very quickly, which is needed in the majority of conveyances in use today. This is because the rotating components are driven at very high speeds causing a high rotational inertia that resists a change in speed. This high rotational inertia also causes a danger when failure of a rotating component occurs, because a tremendous amount of energy is stored in the high speed rotating parts. The resultant spray of hot metal parts can be very difficult to contain, piercing anything in their path.
A modern turbo-shaft engine is certainly smoother and lighter than today's dated reciprocating engines, and with the use of a regenerator, can be fairly efficient for fixed speed applications such as an aircraft propeller or an electrical power generator. Again, the acquisition and processing costs of the exotic materials needed in the turbine section push the cost of the turbo-shaft engine well out of reach for most applications. The use of a regenerator adds even more bulk and cost to the system.
In a turbo-shaft engine, the hot gasses of combustion are required to enter the turbine power section at near-sonic speeds. These near-sonic gas speeds are required to produce meaningful power. Unfortunately, the high velocity of the hot gasses causes a major energy loss due to friction and turbulence, with the parasitic friction loss increasing generally as the square of the velocity.
The aforementioned near-sonic gas speeds are required in the turbo-shaft engine because the gasses must impinge the initial rows of turbine blades at very high velocities to provide a meaningful kinetic energy force to the blades. Subsequent rows of blades produce power using a reaction force that can be compared to the lift produced by air flowing over an aircraft wing. These rows of blades also require a high velocity in the hot gasses. The power produced by the impingement and reaction forces increases greatly with an increase in the speed of the hot gasses. For this reason, turbine engines are designed to use as high a gas velocity as possible just below the velocity that would cause detrimental sonic shock waves to form. There is a substantial energy loss due to the turbulence and parasitic drag caused by these high gas speeds.
The tremendous turbulence caused by the high gas speeds, and the vectoring of hot gasses from blade to blade, also cause a substantial transfer of heat to the turbine power section components, adding to the requirement that they be fabricated from exotic, high temperature materials for adequate strength. In contrast, the present invention, an improved open cycle internal combustion engine, does not utilize a turbine power section. The present invention instead uses confined, shaped rotors that counter-rotate to produce power from the pressure of hot gasses. This rotor system does not require the ultra-high gas velocities needed to produce meaningful impingement and reaction forces, as in the turbo-shaft engine. The relatively low speed of the hot gasses in the power section of the present invention, provides a huge reduction in parasitic drag when compared to the turbo-shaft engine, resulting in a greater economy of operation. The reduced speeds and absence of blade-to-blade vectoring of the hot gasses, provides a reduction in turbulence that also reduces heat transfer from the hot gasses to the metal parts of the power section, providing a greatly reduced requirement for exotic high temperature materials.
The reduced speed of hot gasses in the present invention, when compared to a turbo-shaft engine, is made possible by the use of a unique and efficient counter-rotating rotor system to extract power. This dual rotor system provides a substantially positive containment of the hot gasses of combustion in comparison to a turbine power section, where the gasses flow relatively freely through the blades, losing useful energy in turbulence and drag when vectored from blade to blade. Rotational power in the present invention is produced mainly by the pressure of hot gasses upon the protrusions of confined rotors, rather than by the kinetic and reactive forces utilized in a turbine. This eliminates the need for ultra-high gas velocities with the resultant high amounts of energy loss and heat transfer.
In the present invention, hot pressurized gasses of combustion may be produced by any of a multitude of different fuels, to apply a pressure force to the surfaces of protrusions on counter-rotating rotors that rotate within a closely confining encasement. The surfaces of the protrusions opposite to the surfaces on which the pressure force is applied are in gaseous communication with the atmosphere via an exhaust port. The resultant pressure differential causes the rotors to rotate in the direction of low pressure.
The hot gasses change direction smoothly and infrequently in the power section of the present invention, as opposed to the significant number of vector changes found in a turbine power section. This ease of gas movement provides a reduced amount of drag and turbulence and helps the present invention to provide a dramatic increase in efficiency over present day turbo-shaft engines.
As previously mentioned, the turbo-shaft engine is available only at a very high cost, which limits its use to military and commercial aircraft, military conveyances such as tanks and ships, and large electrical power plants. In these high-end applications, the costs of acquisition and the expensive provision of regeneration is not so much at issue. In addition to the high cost of the exotic materials required, additional costs are incurred due to the turbo-shaft engine's high rotational speeds, which require special bearings and lubrication systems, with no tolerance for error in manufacturing.
In contrast, the power section of the present invention has relatively low rotational speeds, reducing the requirement for special bearings and lubrication systems, thus reducing the cost of manufacture. Additionally, the low rotational inertia present at the lower speeds of rotation allows speed changes to be effected much more easily and quickly when compared to the turbo-shaft engine.
The present invention is simple in structure, with few moving parts, making it significantly less expensive to manufacture than today's reciprocating engines as well. This low cost of manufacture along with an unprecedented efficiency, allows an opportunity for wide-spread use in hybrid automobiles, boats, trains, airplanes, electrical generators, and other usages in which a simple, low cost, highly efficient, clean burning, multi-fuel engine can be of service.